Recently, organic EL display devices (referred to as “OLED display devices”) have been actively developed as display devices including, as light sources, light emitting elements using an electroluminescence (EL) phenomenon. An organic EL display device includes an organic EL element as a light emitting element in each of pixels, and displays an image on a display portion by controlling light emission of the organic EL element.
Such an organic EL element includes a light emitting layer formed of an organic material provided between an anode and a cathode. Since the light emitting layer formed of an organic material is weak against moisture, the organic EL display device usually has a structure preventing entrance of moisture from outside. For example, Japanese Laid-Open Patent Publications Nos. 2011-191739, 2013-84619 and 2009-295911 disclose a technology suppressing deterioration of an organic EL element by moisture.